The candidate is a clinical endocrinologist dedicated to basic science research working under the mentorship of Dr. Janet Rubin for the past 2.5 years, initially as a T32 fellow and currently as junior faculty funded by UNC's prestigious BIRCWH award. In Dr. Rubin's laboratory, Dr. Styner acquired substantial expertise in the study of mechanisms by which mesenchymal stem cell (MSC) differentiation is regulated. Prior work in the Rubin lab revealed that mechanical repression of MSC adipogenesis involves decreased expression of PPAR3; the candidate's own work led to the hypothesis that C/EBP2, a transcription factor expressed early in adipogenesis, might be critically involved in mechanical repression of adipogenesis through regulation of PPAR3. This hypothesis will be tested in SA1, where C/EBP2's role in MSC differentiation will be analyzed using substrate stretch to deliver mechanical input in vitro and using wheel based running exercise in mice in vivo. C/EBP2 and potential regulators will be varied using molecular techniques during the mechanical/exercise input. In SA2 the candidate proposes that mechanical-exercise induced downregulation of C/EBP2 will protect against MSC endoplasmic reticulum (ER) stress. Preliminary data show that MSCs subject to mechanical strain are resistant to the pro-apoptotic effects of ER stress, preventing adipogenesis and preserving MSC potential. Experiments will characterize C/EBP2's role in ER stress in vitro and in vivo and the ability exercise to protect through limiting C/EBP2 expression. An effect of exercise to regulate both adipogenesis and ER stress via C/EBP2 would represent novel mechanisms for salutary effects of exercise. The candidate's short-term career goals include 1) building on her technical skills in molecular biology and acquiring new skills in microscopy and the conduct of animal research including the use of in-vivo exercise models, 2) increasing her strategy and data analysis skills, as well as skills in running a laboratory 3) expanding her knowledge in the field of ER stress and 4) developing her skills in writing and grantsmanship. The candidate's long-term-career goal is to become an independent investigator with expertise in the effects of exercise on fat and skeletal biology with an emphasis on understanding basic mechanisms affected by exercise (MSC differentiation and ER stress). The candidate's primary mentor, Dr. Janet Rubin, is a physician scientist with a record of training young investigators and with an international reputation in the field of mechanical effect in skeletal biology. The co-mentor, Dr. Cam Patterson, has an excellent record of training investigators and will provide Dr. Styner with content area expertise in the field of ER stress. The research environment will provide a productive, supportive and collegial background to pursue the proposed research and to develop an independent career where the candidate intends to bring knowledge of exercise effects on cells to the treatment of chronic diseases such as osteoporosis, frailty and obesity.